10GBASE-T is an Ethernet standard that provides a nominal data rate of 10 Gbit/s over twisted pair cables. A standard 10GBASE-T architecture enables multiple network devices to communicate via a link formed by conventional twisted pair copper wires. The wire-level modulation for 10GBASE-T is a Tomlinson-Harashima Precoded (THP) version of pulse-amplitude modulation with 16 discrete levels (PAM-16), encoded in a two-dimensional constellation pattern known as 128-DSQ (Double Square QAM).
The complex signaling scheme adopted by the 10GBASE-T standard works well for twisted pair cables made of higher quality materials and signal integrity characteristics. However, for lower quality cables, such as category 5 cabling, reaching the nominal data rate of 10 Gbit/s over appreciable distances can be problematic. In circumstances where the signal-to-noise ratio (SNR) for successful link operations is too low, the 10GBASE-T specification requires that the link renegotiate its operation to a mode that is backwards compatible with one or more older Ethernet standards that operate at much lower data rates. Thus, a first reduction in the data rate might occur at a level of 1000 Mbit/s (corresponding to 1GBASE-T), or even 100 Mbit/s. In many circumstances, a category 5 cable may support data rates much higher than 1 Gbps, although less than 10 Gbps. Thus, automatically renegotiating to a low data rate, when in fact a link may support much higher data rates, is inefficient.
Accordingly, what is needed is a system and method that provides more flexibility in scaling the data rates of 10GBASE-T Ethernet channels over various signaling media.